[Bug]: OpenCode w/ Opus 5 fails due to unsupported `thinking.type.enabled`

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/server

Steps to reproduce

1. Configure the OpenCode provider. Select Claude Opus 5.
2. Start a thread and send any prompt. The request fails every time with:

"thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.

Expected behavior

Claude Opus 5 should work through T3 Code's OpenCode integration.

T3 Code should use the adaptive thinking configuration supported by this model, including thinking.type.adaptive and output_config.effort where appropriate.

The same model works correctly when used directly through standalone OpenCode.

Actual behavior

Every request to Claude Opus 5 through T3 Code's OpenCode integration fails immediately with:

"thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.

The error indicates that T3 Code is sending the older thinking.type.enabled configuration for a model that requires adaptive thinking.

This is deterministic and happens on every attempt.

Impact

Blocks work completely

Version or commit

0.0.30-nightly.20260728.936 (2919147c80e4)

Environment

• macOS 26.5.2, Apple Silicon
• Integration: OpenCode 1.18.3
• Model: Claude Opus 5
• Standalone OpenCode works with the same model

Logs or stack traces

"thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.

Screenshots, recordings, or supporting files

Workaround

Use Claude Opus 5 directly through standalone OpenCode instead of T3 Code, or select a different model in T3 Code.

Start in apps/server and trace the OpenCode integration's request construction, searching for the thinking.type.enabled configuration. Reproduce the failure with Claude Opus 5 and compare the outgoing configuration with standalone OpenCode. Done means the model request uses the supported adaptive thinking settings and succeeds through T3 Code.